1). Field of the Invention
Embodiments of this invention relate to an electronic assembly, and more particularly, how electrically connections are made between various components of the electronic assembly.
2). Discussion of Related Art
Integrated circuits are formed on semiconductor wafers. The wafers are then sawed (or “singulated” or “diced”) into microelectronic dice, also known as semiconductor chips, with each chip carrying a respective integrated circuit. Each semiconductor chip is then mounted to a package, or carrier, substrate, thereby forming a semiconductor package. Often the packages are then mounted to a motherboard, which may then be installed into a computing system.
The package substrates provide structural integrity to the semiconductor chips and are used to connect the integrated circuits electrically to the motherboard. Ball Grid Array (BGA) solder ball contact formations are formed on one side of the package substrate and are soldered to the motherboard. Electric signals are sent through BGA formations into and out of the package.
Smaller solder contact formations, such as controlled-collapse chip connections (C4) contact formations, are formed on the microelectronic die and are attached to an opposing side of the package substrate. The electric signals are sent between the package and the microelectronic die through the C4 contact formations.
The package substrate typically has a coefficient of thermal expansion (CTE) that is four or five times greater than the CTE of the die. So that the package expands at a much faster rate than the die when heat is generated as the die is powered up. Differential expansion between the die and the package substrate increases the mechanical stress on the contact formations, which can lead to the contact formation becoming separated from either the die or the package substrate and failure of the package.